It is perfectly normal for a mother to have those kinds of feelings. However in the end, it is a matter of trust in the sovereign will of our God.
As I look at the book of Psalms, I see David lamenting and pleading with God on many occasions. However in the end he trusted God no matter what life through at him.
All we can do in the situation you brought up is make sure we bring our children up in the Lord and trust God no matter what happens.
However, I must say we should not worry about tomorrow, for tomorrow with take care of itself.